The firing of a cartridge in a rifle or other firearm creates tremendous gas pressure within the cartridge case which results in the forceful expulsion of the bullet or projectile inserted in the cartridge case. The explosive force of firing a cartridge, depending on the cartridge, is generally somewhat above 25,000 pounds per square inch and is created so rapidly that the internal pressure generated also expands the cartridge case within the firing chamber of the firearm which retracts only slightly after the pressure is fully released.
Thus the spent cartridge case is stretched, that is, it is both elongated and expanded in diameter. Both of these distortions must be corrected if the cartridge case is to be reloaded for reuse. Reloading of larger caliber cartridges is a popular pastime because the cost of reloading spent cartridges is only a fraction of the cost of new ammunition. Further, the auto-reloading process enables the shooter to devise special loads which are not available in commercial ammunition.
The reloading process begins by first removing the spent cartridge primer and cleaning the case. Thereafter, the cartridge case diameter is resized using a die of correct dimensions and drawing the die forcibly over the cartridge case using a properly designed press. Thereafter, retrimming of the case length is necessary because the case was elongated in the firing process and if it is not trimmed to the proper length, it can cause dangerously high head pressures when reloaded and fired, especially in those cases where maximum powder loading is employed to produce higher muzzle velocities.
The retrimming of the resized spent cartridge returns the stretched cartridge case to its original dimensions and permits the refurbished cartridge to be safely reloaded and used.
Gracey (U.S. Pat. No. 4,686,751) is the most recent to address the problem of trimming spent cartridges for reloading and reuse. However, Gracey's device suffers from two principal defects, namely, it does not accurately redimension the cartridge for reuse because it only factors the expansion occurring between the cartridge shoulder and the cartridge mouth into its trimming operation thereby ignoring the expansion of the cartridge body and leaving the expansion of that portion as an error in the overall sizing; and because Gracey requires a permanent work bench location, to which his device is bolted, in order to function thereby leaving a vast void for those who would prefer to have an accurate case trimmer which is readily transported with the shooter and can be operated manually anywhere the sportsman chooses, irrespective of work benches or electric power source.
Furthermore, the prior art devices required the operation to hold the cartridge case by hand to prevent it from rotating in response to the rotary cutter which often resulted in great hand fatigue and severe cramping of the hand muscles.
It is toward the elimination of these prior art problems that the present invention is directed.